[Note: If you're tired of my recent biodiesel obsession, feel free to skip this post.]
The National Biodiesel Board has issued a response
to the recent Pimentel/Patzek study which claims that biodiesel is a net energy loser. The NBB cites a 1998 study
sponsored by the Departments of Agriculture and Energy which shows a soil-to-wheel positive energy balance (3.2:1) for soy biodiesel when used in an urban bus.
The Secretaries of the Departments of Agriculture and Energy are always people appointed by presidents whose first step towards nomination was the Iowa caucuses and who were elected by the electoral college (which gives inordinate weight to lightly-populated farm states), and whose nominations were confirmed by the U.S. Senate in which some fairly unimpressive farm-staters like Bob Dole and Tom Daschle have wielded large power. So it can be fairly assumed that the USDA and the DOE are going to undertake a study on biodiesel with a bit of a bias towards finding a favorable conclusion.
Still, the 314-page USDA/DOE report is far more thorough than the 12-page P&P study (of which only two pages deal with biodiesel). USDA/DOE also explain their terms in much greater detail, making the crucial distinctions which need to be made to determine whether making biodiesel from soybeans is "renewable" or even worthwhile at all. For example:
The fossil energy ratio tells us something about the degree to which a given fuel is or is not renewable. It is defined simply as the ratio of the final fuel product energy to the amount of fossil energy required to make the fuel:
Fossil Energy Ratio = Fuel Energy/Fossil Energy Inputs
If the fossil energy ratio has a value of zero, then a fuel is not only completely nonrenewable, but it provides no useable fuel product energy as a result of the fossil energy consumed to make the fuel. If the fossil energy ratio is equal to 1, then this fuel is still nonrenewable. A fossil energy ratio of one indicates that no loss of energy occurs in the process of converting the fossil energy to a useable fuel. For fossil energy ratios greater than 1, the fuel actually begins to provide a leveraging of the fossil energy required to make the fuel available for transportation. As a fuel approaches being "completely" renewable, its fossil energy ratio approaches "infinity." In other words, a completely renewable fuel has no
requirements for fossil energy.
, p. 207)
In contrast, Pimentel and Patzek don't define their terms well, and pick and choose whatever they can find to make biodiesel look bad. For example, on page 72 of their report (it's in a journal, so page 72 is actually page 8) they say:
Sheehan and others of the Department of Energy also report a negative energy return in the conversion of soybeans into biodiesel. They report "1 MJ of biodiesel requires an input of 1.24 MJ of primary energy."
This is deception at its worst. First off, Sheehan is one of the authors of the USDA/DOE report which supports biodiesel production. More importantly, unlike P&P, the USDA/DOE report defines what is meant by "primary energy:"
Total Primary Energy. All raw materials extracted from the environment can contain energy. In estimating the total primary energy inputs to each fuel’s life cycle, we consider the cumulative energy content of all resources extracted from the environment.
So "primary energy" includes not only the diesel fuel to run the trucks and tractors used to grow and process the soybeans--it includes the solar energy captured by the soybean plants, and every other form of energy used in the process. P&P cite the 1.24 ratio of primary energy in to energy out as a bad thing, when in fact all it demonstrates is that biodiesel production is not a perpetual motion machine. As the USDA/DOE study points out, the real key, given our current circumstances, is the fossil energy ratio. Actually, I would expand that to be a non-renewable energy ratio, since I'm afraid that one of the main responses to both peak oil and global warming is going to be calls for using more nuclear energy. Nevertheless, the USDA/DOE study is much more careful about defining their terms and pointing out what the real issues are than are P&P.
As I see it, biodiesel wins the argument. If we hope to still have some mechanized ground and air transportation available to us in the future, we'll need energy-dense liquid fuels. We can either grow a bunch of plants and animals, let them die, and wait 50 million years or so for the earth to turn them into oil and coal, or we can grow oil-yielding plants and process them into liquid fuels today in the most efficient way possible. The USDA/DOE report makes a good case that the process can actually be quite efficient in the most important ways, while the P&P study completely fails to disprove that.
Full disclosure: My investment in biodiesel consists of a 2001 Volkswagen Golf TDI, a few stickers, and half a tank of B99 biodiesel. If I could be convinced that biodiesel was actually making things worse, I could switch to running on petrodiesel--it would be easier (more stations) and currently cheaper. But I'll say that a couple of die-hard anti-biodiesel professors have taken their best shot at biodiesel and missed completely, and I'll keep running on biodiesel unless somebody makes a much better case.
For a lengthy summary of my recent defense of biodiesel, go here